Novel Chiral 1,3,4-Oxadiazole Derivatives Inducing Astrocyte Differentiation of Rat Fetal Neural Stem Cells

Full text of DOI:10.1002/bkcs.11647

Communication
DOI: 10.1002/bkcs.11647
BULLETIN OF THE
J. Song et al.
KOREAN CHEMICAL SOCIETY
Novel Chiral 1,3,4-Oxadiazole Derivatives Inducing Astrocyte
Differentiation of Rat Fetal Neural Stem Cells
†,
Jiho Song,† Dong-Wook Kim,‡ Jiho Jang,‡, and Kyung Hoon Min
*
*
†College of Pharmacy, Chung-Ang University, Seoul 06974, Republic of Korea.
*E-mail: khmin@cau.ac.kr
‡Department of Physiology, Yonsei University College of Medicine, Seoul 03722, Republic of Korea.
*E-mail: jhjang@yuhs.ac
Received November 19, 2018, Accepted November 26, 2018
Keywords: Neural stem cell, Astrocyte, Small molecule, Chirality, 1,3,4-oxadiazine
Neural stem cells (NSCs) are multipotent cells that can dif-
ferentiate into neurons, astrocytes, or oligodendrocytes. The
primary focus of research on NSCs has been their neuronal
differentiation to treat neurodegenerative diseases including
Alzheimer’s disease and Parkinson’s disease.1,2 Many
efforts have been made to drive NSCs toward a neuronal
fate, not only using transcription factors but also small
molecules.3–5 However, there have been only a few studies
reporting the differentiation of NSCs into astrocytes. Astro-
cytes are the most abundant cell type in the brain.6 Astro-
cytes are found to be multifunctional cells that play critical
roles in the development of neurons, maintenance of cellu-
lar homeostasis, and energy supply.5 Furthermore, they
form in the brain together with pericytes, endothelial cells,
and adjacent neurons the blood–brain barrier.5 As the
knowledge about the role of astrocytes expanded, the
importance of astrocytes in neurodegenerative diseases
started to emerge. Thus, neuroscience research might bene-
fit from small molecules that regulate the fate of NSCs.
We reported that 1,3,4-oxadiazole derivatives induce the
differentiation of rat fetal neural stem cells into astrocytes.7
The previously reported compounds were racemic mixtures.
The stereochemistry of small molecules is very important
for their biological activity. The enantiomers of many chiral
drugs have been reported to show different biological activ-
ities.8 Thus, we tried to explore the activity of the stereoiso-
mers of 1,3,4-oxadiazole derivatives.
differentiation. The desired compounds were readily syn-
thesized from N-Boc phenylglycines, a commercially avail-
able chiral building block, as starting materials using the
same methods as described previously (Scheme 1).7
An image-based assay was performed as reported
previously,7 which revealed that the (S)-isomer of com-
pound 1 induces the differentiation of rat fetal neural stem
cells into astrocytes (data not shown). The racemate of ben-
zamide compounds 5 derived from 1 exhibited an increased
activity for astrocyte differentiation. The (S)-isomer (S)-59
of the benzamide analogue showed a significantly increased
activity for astrocyte differentiation compared to the (R)-
isomer (R)-5 (Figure 2).
An additional evaluation of compounds (S)-1, (S)-5, and
(R)-5 was conducted using real-time (RT)-PCRs of markers
for astroglia (GFAP and S100), neurons (β-tubulin), and
Therefore, we synthesized the derivatives of compound
1 (Figure 1). A set of S- and R-enantiomers was prepared
to determine their stereospecific activity on NSC
Scheme 1. Synthesis of 1 and 5. Reagents and conditions:
(i) benzhydrazide, CDI, CBr4, PPh3, DCM, 0 ꢀC, 66–78%;
(ii) TFA, DCM, rt., 2 h, 99%; (iii) compound (S)-1: Phenylacetyl
chloride, THF, rt., 5 h, 99%, compound 5: Benzoic acid, DMAP,
EDC, DCM, rt., 4 h, 26–48%.
Figure 1. Structure of compound rac-1 and its stereoisomers.
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the expression of astroglial markers while the correspond-
ing (R)-isomer did not significantly influence neuronal and
astroglial markers. This study demonstrates that the chiral-
ity of (S)-5 was an important factor for its activity in astro-
cytogenesis and could be a chemical tool for stem cell
researches.
Figure 2. Representative immunofluorescence images of GFAP
(astrocyte marker, green), DAPI (nuclei, blue), and β-tubulin(neu-
ral marker, red) of NSCs treated with DMSO, (S)-5, or (R)-5.
Acknowledgments. This work was supported by the
National Research Foundation of Korea grants (NRF-
2015R1A5A1008958, NRF-2015R1D1A1A01058923 and
NRF-2018M3A9F8065834) funded by the Korean
government.
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S100
Figure 3. Relative mRNA expression levels of GFAP, S100,
β-tubulin, and nestin after the treatment of astrocytes with (S)-1,
(S)-5, and (R)-5, which were analyzed using quantitative real-time
PCR.
Data
present
mean Æ SEM.
Student
t
test,
*P < 0.05, **P < 0.01.
neural stem cells, progenitors, or neurons (nestin). Treat-
ment of NSCs with (S)-5 significantly increased the expres-
sion of both astroglial markers more than 2-fold compared
to DMSO used as vehicle control, while (S)-1 and (R)-5
induced only 1.2- and 1.3-fold increases, respectively
(Figure 3). Furthermore, (S)-5 did not enhance (or slightly
decreased) the expression of β-tubulin and nestin
(Figure 3), while (R)-5 slightly and significantly increased
the expression of these neuronal markers.
In summary, we identified (S)-5 as a potent small mole-
cule regulator for the selective differentiation of NSCs into
astrocytes. The activity of (S)-5 for the differentiation of
NSCs into astrocytes was validated by image-based assay
and RT-PCR. Only the (S)-isomer (S)-5 potently increased
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(phenyl(5-phenyl-1,3,4-oxadiazol-2-yl)methyl)benzamide ((S)-
5). 1H NMR (600 MHz, DMSO‑d6) δ 9.74 (d, J = 7.8 Hz,
1H), 7.97 (t, J = 6.8 Hz, 4H), 7.66–7.54 (m, 6H), 7.51 (t, J =
7.6 Hz, 2H), 7.45 (t, J = 7.5 Hz, 2H), 7.40 (d, J = 7.2 Hz, 1H),
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